Retaining means for sphygmomanometer valve control head

ABSTRACT

An improved control mechanism for a self-closing sphygmomanometer valve is disclosed. The valve head is movable from an upper closed position to a lower open position against the action of an internal spring. The internal chamber of the valve head is narrowed at its upper portion to achieve a wedging fit over the enclosed valve guide, to thereby selectively retain the head in a depressed position from which it can be released by the application of a lateral force by the operator.

United States Patent 1191 Hayes 1 1 RETAINING MEANS FOR SPHYGMOMANOMETER VALVE CONTROL HEAD Roger Hayes, 260 Garth Rd., Scarsdale, NY. 10583 Filed: Sept. 14, 1972 Appl. No.: 289,149

lnventor:

[52] U.S. Cl l28/2.05 G, 137/515, 251/93, 251/285 [51] Int. Cl A6lb 5/02, Fl6k 51/00 8] Field of Search... 128/205 G, 2.05 C, 2.05 M, 128/205 0; 251/285, 92, 93, 145; 137/515, 516.13

[56] References Cited UNITED STATES PATENTS 4/1960 Speelman l28/2.05 o 7/1962 Noland 251/285 x l/l964 Price 251/285 x 1 1 July 16, 1974 3,254,671 6/1966 Berliner 128/205 (1 3,361,148 1/1968 Turek 251/285 X 3,504,663 4/1970 Edwards 123/205 G 3,738,357 6/1973 Hayes 128/205 G Primary Examiner-Kyle L. Howell Attorney, Agent, or FirmGottlieb, Rackman & Reisman [5 7] ABSTRACT An improved control mechanism for aself-closing sphygmomanometer valve is disclosed. The valve head is movable from an upper closed position to a lower open position against the action of an internal spring. The internal chamber of the valve head is narrowed at its upper portion to achieve a wedging fit over the enclosed valve guide, to thereby selectively retain the head in a depressed position from which it can be released by the application of a lateral force by the operator.

' '5 Claims, 8 Drawing Figures PATENTEU JUL 1 s 1914 SHEEYIOFZ I RETAINING MEANS FOR SPHYGMOMANOMETER VALVE CONTROL HEAD This invention relates to valve members for sphygmomanometers, and in particular, to an improved control mechanism for such valves.

As expalined in my copending application Ser. No. 192,193, filed on Oct. 26, 1971, which application is incorporated herein by reference, and which is now US Pat. No. 3,738,357, existed in prior art valve mechanisms in general, and in control valves for sphygmomanometers in particular. Among these problems are the difficulty of manipulation of whatever valve control member is utilized (e.g., rotational sleeves, spring-loaded buttons, etc.) all these prior art arrangements are analog innature and all are dependent on the skill and dexterity of the operator. A problem has also been posed by the inability of the prior art to establish pre-settable release rates for sphygmomanometer valves. Such discrete rates could provide each oerator, whether a doctor, nurse or hospital technician, with a release rate from a valve which is suitable to his own reading desires and capabilities. There is also a significantneed for repeatable release rate valves in automatic" blood pressure machines, for example.

These problems were largely solved by the invention and development of the cam control member as disclosed in the above-identifiedcopending application. That application discloses a vertically movable head whose stroke distance is controlled by the setting on the underlying eccentric cam with which it comes in contact on its downward movement. Rotating the cam about the valve body controls the extent to which the head moves downward vertically, since the cam is eccentric with respect to its axis of rotation about the valve body and provides a range of contact points for the head to be stopped by. The downward movement of the head, in turn, controls the extent of the opening of the valve stem, with a greater downward movement opening the valve stem cavity to a greater degree, thereby permitting the pressurized fluid to escape at a more rapid rate than would be permitted if the valve head were to be able to move downward only a relatively shorter distance.

The previous application was also addressed to the problem of providing a quick release arrangement for valves, whereby following the completion of a blood pressure reading cycle, the air remaining in the blood pressure cuff could be removed rapidly without significant operator attention, thereby permitting the device to be immediately ready for subsequent runs. This problem was overcome in the prior application by providing a beveled surface-on one outer side of the movable valve head. When it was desired to remove any remaining air from the cuff, the valve head would be rotated about its longitudinal axis, thereby bringing the beveled surface over the underlying cam; greater downward movement of the valve head would be possible in this position and would bring the beveled surface thereon into wedging engagement with the upper edge of the cam, providing a retention position for the valve head at its lowermost valve release point. During this unattended release mode, the operator did not need to pay any attention to the deflation of the valve, and by the time a previous reading had been suitably recorded,

the mechanism was ready for a new measurement cycle.

The foregoing structural advantages were and are significant improvements over the prior art, and are among the principal novel features of my invention. 1 have now designed certain refinements of my earlier invention, including structural revisions of the cam and the valve head retaining means, as well as providing for a unique check valve to make for easier inflation and fully functional for its desired purpose, and it is fully described in the copending application. But-it has been determined that it would be desirable to have a cam which is even more versatile insofar as it would more securely retain its rotational setting and yet still permit an operator to change the setting without requiring separate adjusting equipment. Another significant factor is the ease of assembly of the cam as a part of the overall valve mechanism it is advantageous for the cam to be in a form which permits mounting on the valve body during the course of manufacture without any great difficulty.

It is therefore an object of this invention to provide 7 an improved cam arrangement to act as a limit stop for a valve head.

It is also an object of this invention to furnish a cam whose stoppositions with respect to the valve head can be securely set and yet adjusted by an operator without the need for auxiliary tools. v

It is afurther object of this invention to supply a cam in a form which permits ease of assembly and mounting ance on the wedging engagement between the external beveled surface of the valve head and the cam edge is quite effective. However, such an arrangement is based on a completely external contact between the head and the cam, and accordingly, this may cause unsightly wear to the valve head.

It is therefore another object of my invention to provide easily fabricated internal means for retaining a valve head in a fully depressed position, while still furnishing complete capacity for the head to be readily released.

In the copending application, a conventional check valve is illustrated for allowing inflation of a blood pressure cuff in one direction and for preventing the leakage of pressurized fluid in the other direction once inflation has been-achieved. This feature, too, is fully operational in the disclosed embodiment. While fulfilling the desired criteria for a check valve, it would be more advantageous for'such a valve to open more readily during'the inflation step, to seal more securely and rapidly when the cuff pressure builds up to a point where it exceeds the inflation pressure being applied and to achieve these advantages'without the need for a spring or other internally contained closing device.

It is therefore another object of this invention to provide an improved check valve for more secure sealing against the escape of pressurized fluid and to reduce the inflation pressure needed to overcome the check valve sealing arrangement during the inflation step, i.e., to reduce the back pressure due to check valve resistance.

These and other objects and advantages of the invention will become apparent when a particular illustrative embodiment thereof is considered, wherein improved valve head retaining means, gripping cam and check valve arrangements are disclosed. As in the copending application, the valve head is movable along a vertical axis and is normally maintained in an upper position at which point the valve stem, which is coupled to the valve head, completely occupies its valve stem cavity, thereby closing off the valve and preventing any flow of air from the blood pressure cuff out to atmosphere. The valve head may be generally cylindrically shaped, with aflattened side surface in the case of a cylindrical valve head, a typical side surface shape would be a rectangle, formed by the intersection of the cylindrical valve head with a vertical plane. During normal use when blood pressure readings are being taken, the valve head is disposed with its flattened surface away from the underlying cam. This mode of operation causes the valve head, upon depression, to have its bottom surface come into contact with the cam. As the valve head is depressed, its valve stem also moves downward a corresponding distance, thereby opening the valve stem cavity and permitting pressurized fluid to flow from the inflated cuff through the valve body and out to atmosphere through an aperture in the valve head.

The valve head is normally maintained in its upper closed position by an internally contained spring, housed in a cavity within the valve head. In order to achieve a rapid deflation mode with no operator attention, the spring-contained cavity within the valve head has its upper bore narrowed so that it is formed in a frusto-conical shape. Upon depression of the valve head, this narrowed bore within the valve head comes into contact with the upper rim of the valve guide, causing a removable yet snug fit for the valve head. The valve head will remain in its wedge contact position with the valve guide under normal conditions without any further intervention by an operator. Deflation thereby occurs without further operator involvement and at a relatively rapid rate.

In order to dislodge the valve head, a lateral or rocking action may be applied thereto, and this relatively simple but firm force causes the narrowed bore to be loosened from contact with the upper edge of the valve guide, and the expansion action of the internally contained spring drives the valve head upwards to its normal closed position. During the time when the valve head was retained in its downward position, however, the valve stem cavity was fully open, and the pressurized fluid from the inflated blood pressure cuff thereby escapes at a rapid rate through the valve bore, the valve stem cavity, the valve stem passageway, the valve guide and outv to atmosphere through the spring chamber within the valve head. This provides the specified rapid and unattended deflation of the blood pressure cuff.

The various presettable rates of deflation are controlled by the setting of the eccentric gripping cam mounted on the valve body. This arrangement is based upon the fact that as the valve head is depressed by an operator, its lower surface will come into contact with the upper edge of the cam after having travelled a distance dependent upon the rotational setting of the cam. The distance which the valve head has travelled controls the opening provided by the valve stem which is coupled to the valve head the greater the distance travelled by the valve head, the greater the opening of the valve stem and the release rate of pressurized fluid. The cam can be rotatably set around the valve body to provide a range of presettable release rates which can accommodate the desires and capabilities of all technicians and operators.

The present invention provides for securely retaining the particular presettable value selected by an operator, by utilizing a gripping cam constructed to exert a spring-like force onthe valve body on which the cam is mounted. Together with ths spring-like force, the cam is designed with a pair of spaced adjustment nodes which have been designed to present an area substantially as large as possible to an operator. The angle of the nodes has also been designed so that when the usual perpendicular force is applied by the operator, it will be in a direction opposite to the line of maximum apparent friction force retarding movement of the cam. This helps the operator to overcome the spring-like force holding the cam in place, allowing an easier adjustment of the cam s rotational position. This facilitates the adjusting of the rotational position of the cam without the need for utilizing auxiliary tools or equipment; yet the spring force applied by the cam itself will resist most casually applied forces which are not directly intended to change the rotational setting of the ring, and will resist such forces unless they are correctly applied to the adjustment nodes. The adjustment nodes are also designed to occupy the maximum moment arm with respect to the center of rotation of the ring, thereby serving to permit the spring force of the cam to be more easily overcome by the application of pressure to the adjustment nodes. The design of the cam, with the adjustment nodes spaced to form a passageway therebetween, allows for mounting of the ring over the valve body and facilitates installation of the ring in the groove provided therefor on the valve body.

The check valve utilized in this invention makes use of the largest cross-sectional area for the bore in the check valve assembly that can be accommodated within the valve design. On the side of the check valve from which inflation pressure emanates, the employment of this larger bore than previously used will result in the application of a relatively greater force to a larger freely riding self-contained check valve member, due to the principle of force being'equal to the applied pressure multiplied by the area against which the pressure is applied. The new larger check valve member itself can take the form of a disc having a diameter nearly as great as the main portion of the valve body, which freely rides within the check valve cavity. On the other side of the check valve member, i.e., the side closest to the cuff and pressure release path, the central bore through the valve body transmits the pressure from the cuff to the enlarged check valve, tending to force it closed. At such times, following the same principle enumerated above, the back pressure applied from the cuff against the check valve member will be exceedingly large, particularly when the pressure in the cuff is high. Accordingly, when the cuff has been suitably inflated to a pressure sufficiently in excess of that at which the pressure release and reading cycles may be commenced, the back pressure applied against the check valve member will be quite high and will securely prevent any of the pressurized fluid from escaping back along the inflation path. At the same time, before this inflation point has been reached and while the inflation step is still being carried out, the large bore on the inflation side of the check valve member and the absence of any spring minimize operator effort in inflating the cuff.

As can therefore be appreciated from a consideration of the foregoing aspects of this invention,'there are a number of operational features in common with the copending application Ser. No. 192,193, filed on Oct. 26, 1971. The principal areas of patentable distinction between this application and the prior application, however, are in the means for retaining the valve head in its fully depressed quick deflation mode, the design and operation of the gripping cam and the use of a novel check valve arrangement. As has been previously noted, all of the counterpart features disclosed in my copending application are fully functional and operational; however, it is believed that the specified features in the present application constitute novel improvements which will enhance the operation of the inven-.

tion structure and other similar valves.

It is therefore a feature of an embodiment of this invention that a cam acts as a stop for a movable valve head and retains its rotational positionabout the valve body by spring action unless positively adjusted by an operator;

It is also a feature of an embodiment of this invention that a cam,'acting as a limit stop, is formed as an open ring to provide for easier mounting on a valve body and for the optimum distribution and direction of applied forces to the ring.

It is a further feature of an embodiment of this invention that an internally narrowed bore of a movable valve head is engaged with a valve guide to provide a secure retaining position to establish a rapid deflation mode of operation, and from which an operator can dislodge the head by lateral movement thereof.

It is another feature of an embodiment of this invention that a check valve in the inflation path of a pressure control mechanism is made substantially as large in surface area as can be accommodated within a comparably large bore, to provide the greatest force against leakage through the inflation path and at the same time provide for greater ease of inflation operation.

These and other objects, features and advantages of this invention will become more readily understood when considered in connection with a presently preferred, but nonetheless illustrative, embodiment of the invention as explained in the following detailed description and as shown in the accompanying drawing, wherein:

FIG. 1 is an overall perspective view of the control mechanism of the invention;

FIG. 2 is a fragmentary side sectional view of the control mechanism illustrated in perspective in FIG. 1, taken from the perspective of line 2--2 of FIG. 1 in the direction of the arrows;

FIG. 2a is a sectional view of the check valve member, taken along the line 2a-2a of FIG. 2 in the direction of the arrows;

FIG. 3 is an enlarged fragmentary view of the valve head of the invention rotated to a position where it can be depressed fully into the wedged rapid deflation mode;

FIG. 4 is an end view of the valve mechanism, partly in section, illustrating the relationship among the gripping cam, valve body and valve head, taken from the perspective of line 44 of FIG. 1 in the direction of the arrows;

head to be depressed therethrough without requiring the normal rotation of the valve head;

FIG. 6 is an end view of the valve mechanism illustrating the relative positions of the cam and valve head shown in FIG. 5; and

FIG. 7 is an enlarged showing of the illustrative shape of the cam of the invention.

Initially referring to the overall perspective view of the invention illustrated in FIG. 1, the operation of my improved invention is generally comparable to the manner of operation of the invention disclosed in copending Application Ser. No. 192,193, filed Oct. 26, 1971, which has previously been incorporated herein by reference. In particular, the valve control arrangement l0 incorporates a vertically movable head 12 which isillustrated as being cylindrical in shape, but

on selected downward movements of valve head 12, as will be described below. In normal use, when readings are to be taken by an attendant, cam 14 functions to' intercept valve head 12 in its downward movement, by contact between the bottom surface 12a of valve head 12 and the upper edge of cam 14. The extent of the depression of valve head 12 in turn controls the opening of valve stem 28b attached to the valve head, thereby governing the release rate of the pressurized fluid from the blood pressure cuff represented by block 17.

.T he main bore of the valve 10 is contained within valve body 16, and connecting tube 18 links up with blood pressure cuff in conventional fashion. Inflation is provided by means of bulb 22, which is squeezed by the attendant, thereby furnishing air under pressure throughbulb throat 20 and into the main bore through valve body 16. As will be described in greater detail below, the attendant has initially set cam 14 at a rotational position which will establish the distance through wiich'valve head 12 can travel downwardly during the pressure reading cycle as the pressurized air is released from the blood pressure cuff. Accordingly, after a suitable inflation pressure level has been reached as determined by the operators reading the pressure gauge (not shown), the valve head 12 is depressed against spring 36, thereby causing bottom surface 12a to ultimately come in contact with the upper edge of cam 14 as valve head 12 moves downwardly.

When such contact has been established, and is maintained by the operator, the pressurized air is released at the preselected rate from the blood pressure cuff (e.g., block 17), escaping through tube 18, the bore within valve body. 16, through the valve stem passagethrough aperture 38 in valve head 12. As the pressure.

is gradually reduced in this manner, the operator is in a position to make the desired systolic and diastolic blood pressure readings by noting the appropriate pressures on a gauge. Whether contact between valve head 12 and cam 14 is maintained continuously or only periodically during the reading cycle, the depression of the head into contact with the cam establishes the predetermined rate of release of pressurized fluid selected by the operator in charge of the device. This rate will continue throughout this particular cycle as long as head 12 is in contact with cam 14. This general mode of operation is substantially the same as was described in the previously mentioned copending application.

The New Gripping Cam of this Invention The cam feature of the present invention which constitutes an improvement over the copending application is best illustrated herein in FIGS. 1, 4 and 7. It is noted that cam 14 not only has a central opening as before, but now is provided with a pair of opposing manipulative surfaces or nodes 14a. The nodes 14a are substantially flattened surfaces which the operator can conveniently manipulate so as to change the rotational setting of cam 14 when desired, by the application of suitable force. The geometry of cam 14 is such that the force applied by the operator to a node is applied in an optimum manner so as to overcome the spring-induced friction forces exerted by the cam in its contact with valve body 16.

Thus, as illustrated in FIG. 2, cam 14 is mounted within a groove therefor in valve body 16. Cam 14 is desirably constructed of spring-type material, which causes it to exert a relatively strong gripping force around valve body 16 after ithas been placed within its accommodating groove. The nodes 140 are substantially aligned with respective radii 14d of cam 14, which is a line from the center of rotation of cam 14 through the point 14d, at which the greatest average friction forces appear to be concentrated this point can be empirically determined. When an operator desiresto shift the setting of cam 14 to establish a different predetermined release rate, he is essentially compelled to apply the moving forces as indicated by the arrows 15 perpendicular to node surfaces 14a in FIG. 7. Those arrows are, in turn, perpendicular to radii 14d, thereby minimizing the force which it is necessary for an operator to apply to nodes 14a in order to overcome the friction forces and to adjust cam 14.

. The geometry of cam 14 is also further arranged advantageously to permit ease of operation of the invention. Thus, nodes 14a are located so as to provide the maximum moment arm 140 with respect to the center of rotation of the cam, and also to provide the maximum moment arm Me with respect to the gripping forces exerted around valve body 16 by virtue of the spring grip of cam 14. In addition, nodes 14a are made long so as to minimize the back pressure created for a given applied force. Accordingly, the overall geometry of cam 14 is such that while the gripping forces applied by the cam to valve body 16 will be significant and will be difficult to overcome without an express attempt to do so, the practically compulsory application of force perpendicular to radii 140 along node surfaces 14a, coupled with the maximum moment arms 140 (with respect to the center'of rotation) and 14d (with respect to the spring gripping force), all cooperate to overcome the secure setting of cam 14 and provide adjustment control over the setting of the cam when an operator desires to adjust the setting.

The Head Retaining Means My previously mentioned copending application disclosed means for retaining the valve head in its lowermost position to permit an operator to achieve an unattended quick release mode of operation. This would normally be done when the pressure reading cycle has been completed, and there is no longer any need to maintain the blood pressure cuff in its partially inflated condition. In order to permit the cuff and the entire valve device to be ready for the next inflation and pressure reading cycle, the operator will generally want the cuff to be deflated; on the other hand, he will not gen erally want to be involved in the actual release of pressurized air from the cuff. Accordingly, the copending application disclosed a beveled or angular surface cut from the valve head, which surface would be rotated into position over the cam and then wedged into secure contact with the cam, thereby retaining the valve head in its lowermost position. This position corresponded to a large opening of the valve stem, causing pressurized air to be released from the cuff at a fast rate, leading to prompt deflation of the cuff. However, as noted above, the present invention includes an improvement over this valve head retaining arrangement.

Referring particularly to-FIGS. 1, 2, 3 and 5, it is noted that substantially uniform flattened surface 12b is present on one side of cylindrical valve head 12. During normal use, as illustrated in FIGS. 1 and 2, surface 12b is disposed opposite to the position of cam 14; during such normal use, the depression of valve head 12 will cause it to come in contact with cam 14 as explained above, establishing the predetermined release rate previously set by the particular operator. However, for the unattended deflation mode, valve head 12 is rotated on its vertical axis, bringing flattened surface 12b into the position illustrated in FIG. 3. When valve head 12 is now depressed by the attendant, the narrower segment of bottom surface 12a of valve head 12, which had previously been on the side away from cam 14, will be adjacent to cam 14; as shown in FIG. 3 in particular,

as valve head.12 continues to be depressed, there will be no contact established between surface 12a and the upper edge of cam 14. Instead, head 12 will bypass cam 14 and continue to move downward over underlying valve guide 40.

The internal structure of valve head 12 provides a chamber 34 for housing spring 36, which is adapted to be compressed between lower surface 340 (which is actually the upper surface of valve guide 40) and the upper surface 34b of chamber 34 as head 12 is depressed. Chamber 34 is also providd with internal constricted bore 34c, which acts as the engaging means with the upper outer circular'edge 40b of valve guide 40. As shown in FIG. 3, as valve head 12 is depressed beyond theposition at which surface 12a would normally come in contact with cam 14, surface 34c comes into contact with outer rim or edge 40b of valve guide 40. Valve head 12 thereby is releasably engaged with valve guide 40, with sufficient engaging force to overcome the expansion of now-compressed spring 36. (It is also noted that comparable engagement between head 12 and guide 40 can be achieved by forming the base of guide 40 (where it joins with valvebody 16) with a frusto-conical portion which is contacted by the lower opening of chamber 34 when head 12 is depressed.)

The retention position for valve head 12, illustrated in FIG. 3, will be maintained through normal use for so long as it is necessary to permit deflation. Deflation occurs, as shown in FIG. 2, when valve head 12 is depressed and thereby drives valve stem 28, coupled to head 12 by set screw 28a, and its associated enlarged illustratedin FIG. 3. Often, this lateral force will be applied by the attendants use of the thumb and forefinger in an alternating fashion, although-each operator will obviously establish his own method of applying the lateral force to valve head 12 to dislodge it after the unattended deflation cycle has been completed. The dislodging of valve head 12 from the engaged position with valve guide 40 will permit spring 36 to resume control over the vertical position of valve head 12 and 1 will thereupon force valve head 12 upward, back to the position illustrated in FIGS. 1 and 2.

The Check Valve Feature During the inflation cycle, it is important for there to be case of inflation for convenience of operation by the attendant; similarly, during the deflation cycle, there is a corresponding need for the inflation cycle not to be reversed,- i.e., that there be security against anyleakage of the pressurized air over the previously used inflation path. This has generally been accomplished in prior art devices, and in the copending application, by a simple check valve which was accommodated within a narrow bore within the valve body. Referring to the prior application identified above'in particular, there was disclosed a projectile-shaped check valve having a conically shaped surface which came into contact with a circular hole on the inflation side of the valve when deflation was occurring; during inflation, the inflation pressure from the bulb drove the check valve member back toward the retaining wall provided by a fixed cup. As previously noted, this arrangement was entirely satisfactory and workable, but not as desirable as that disclosed hereinbelow. v

As shown in FIGS. 2 and2a, the present invention discloses a substantially larger and 2valve member 46. This member is lodged within a correspondingly enlarged check valve chamber 16d nearly as large in diameter as valve body 16.. On the inflation side of the valve (toward the right in FIG. 2), inflation pressure enters the valve through oversized bore 16a. This causes any given applied pressure to create a greater force against the larger area to the right of check valve member 46.

This force, which is substantially greater than any comparable check valve force which has previously been available, gives an operator the capacity to readily overcome the free-riding position of check valve member 46 within chamber 16d, even as the inflation pressure becomes nearly equalized by the gradually increasing back pressure from the cuff. During this inflation step, check valve member 46 is driven to the left in FIG. 2, causing its projections 46a to come into contact with the left vertical wall of chamber 16d this contact prevents bore 16c from being sealed off.

The operation of check valve member 46 is generally similar when inflation has been completed, but before deflation has commenced or while it is going on (but between applications of inflation pressure). In particular, it is critical at this time for there tobe no leakage of pressurized air past check valve member 46 and toward inflation bulb 22, which does have access to the atmosphere. Back pressure is applied through bore 16c of valve body 16, and because of the larger area of check valve member 46 provided herein, a larger and substantial force is developed, causing check valve member 46 to be driven to the right in FIG. 2, causing it to come into tight contact with ridge or valve seat 163. This establishes a tight and secure position for check valve member 46 during the pressure reading and deflation cycles, and also minimizing any leakages which might otherwise be caused by the presence of foreign particles between member 46 and seat 16g.

A Typical Operational Cycle The Setting of Cam 14 As is also explained in my copending application, the

setting of cam 14 will depend in large measure on the rate at which the attendant desires pressurized air to be released, and also on the individual dexterity of that particular attendant during the pressure release cycle. In general, the-attendant will set cam 14 by rotating it inits accommodating groove in valve body 16, so as to bring its narrowest portion beneath valve head surface 1211 if a high rate of release is desired, or to bring its widest radial distance beneath valve head surface 12a if a lower release rate is desired. It will be apparent to those skilled in the art that graduated release rates will 'be obtained by varying the rotational setting of cam 14 between these tWO extremes.

One of the advantages of the improved cam 14 reing application. By fabricating cam 14 of suitable spring metal or comparable resilient material, the spring-like gripping forces previously discussed will cause cam 14 to be securely fastened to valve body 16 in its accommodating groove. The camwill be mounted on the valve body 16 with a conventional retaining ring mounting tool. In particular, the cam will pass over the valve body 16 by spreading the upper portion of cam 14 with a. retaining ring tool whose jaws have been inserted into holes 14b adjacent to nodes 14a," cam 14 will then snap into place in'its accommodating groove in valve body 16. Accordingly, the mounting of cam 14 on valve body 16 will have been accomplished easily with a readily obtainable and conventional tool.

To set cam 14, the attendant applies force substantially in the direction indicated by one of the arrows 15 which is perpendicular to its respective node surface 14a in FIG. 7. This applied force overcomes the existing friction forces and cam 14 can be rotatably adjusted around valve body 16 to establish the particular attendants desired predetermined release rate. By applying the force in the directions indicated, the most effective use of the attendants force will be achieved to overcome the spring-like gripping force applied by the cam 14 to the valve body 16. In adjusting cam 14, node surfaces 14a serve as a type of button of maximized area, insofar as they furnish the attendant with a surface against which to apply the adjustmentforce; because of their shape and angle relative to the hypothetical average friction force radius 14d, when force is applied perpendicularly to node surfaces 14a, the adjustment of cam 14 will be readily accomplished by the attendant. On the other hand, the inadvertent application offorce in any other manner (e.g., around the outer perimeter of cam 14) will generally not result in any change of position of cam 14.

The dimensions ofthe cam 14 along the variable radii around its perimeter range from the widest dimension X to the narrowest dimension Y. If cam 14 is rotatably set so that dimension X resides immediately beneath valve lead contact surface 12a, then the release rate established when valve head 12 is depressed into contact with cam 14 will be relatively low. If, on the other hand, cam 14 is rotated such that dimension Y is disposed beneath contact surface 12a, then the downward stroke of valve head 12 will be greater and the release rate established by the valve will be correspondingly higher.

The release rate selected by a particular operator will depend on how fast he wishes the pressurized air to be released from the cuff, whether the pressure reading cycle is achieved by continuous depression of the valve head 12 in contact with cam 14, or whether the valve head is stepped down, by repeatedly depressing valve head 12 into contact with cam 14 and then releasing it back to its normal position, thereby enabling the attendant to zero in on the critical pressure reading points. The setting of cam 14 illustrated in FIG. 4, for example, is an intermediate position, with the ring being set somewhat closer to its narrowest dimension Y, thereby establishing a relatively high (but not the highest) release rate for the valve.

Inflating the Cuff The Check Valve Feature over the larger area provided by this invention or the right surface of check valve member 46 as shown in FIG. 2. This causescheck valve member 46 to be driven .to the left, until its projections 46a come-into contact with the left wall of check valve chamber 16d within valve body 16. This establishes an inflation path for the air coming from bulb 22 through connecting tubing 20, whereby the air passes through bore 16a, around ridge 16g and check valve member 46 and into valve'bore 160 via check valve chamber 16d. The air passes to the left as indicated by the solid arrows within rives at the blood pressure cuff where inflation is achieved.

When the pressure build-up is relatively low, the inflation pressure provided by the attendants squeezing of bulb 22 will readily overcome the lesser back pres sure from the cuff applied from left to right against check valve member 46 in FIG. 2. However, as this pressure builds up, there will come a point where the cuff pressure exceeds the normal pressure applied by the operator in squeezing bulb 22. While this serves the advantageous purpose of securely urging check valve member 46 against ridge 16g to prevent leakage of pressurized air from the cuff, it is also necessary that the check valve permit inflation to continue despite the build-up of pressure in the cuff as just described. This capability is included in the present check valve feature of my invention because of the use of an enlarged check valve member 46, and a correspondingly wide bore 160 on the inflation side of valve body 16. Thus, although the enlarged check valve member 46 is driven to the right against ridge 16g when the pressure in the cuff builds up, the application of further inflation pressure by the squeezing of bulb 22, when applied over the large area of check valve member 46, provides a substantial force from right to left against check valve member 46, thereby moving member 46 to the left of chamber 16d and permitting the inflation step to continue.

It may therefore be appreciated that the use of a larger sized check valve member 46, together with an appropriate accommodating chamber 16d and an enlarged inflation bore 16a, combine to give the operator great ease of inflation and also to more positively prevent the leakage of pressurized air from the cuff as pressure is built up therein. During inflation, the application of pressure against the right-hand surface of check valve member 46 causes a relatively greater force to be applied to the check valve member in a right to left direction in FIG. 2; during the pauses between the repeated squeezings of bulb 22, and also after the inflation step has been completed, the back pressure from the cuff, applied to check valve member 46 through bore 16b, 160 of valve body 16, will create a sufficiently substantial left-to-right force against check valve member 46 to obviate the need for any auxiliary closing force, such as that provided by a spring. This feature therefore provides ease of inflation and security against leakage of pressurized air.

The Pressure Reading Cycle whereby the blood pressure cuff would be sufficiently bore 16b and connecting tubing 18, and ultimately arinflated, as also described above, the pressure reading cycle can commence. The invention includes the ca pacity to permit an attendant to continuously reduce the pressure, thereby resulting in a substantially uniform reduction in the pressure in the cuff past the systolic and diastolic pressure points, or the operator can also step down the pressure in discrete and discontinuous steps, permitting under some circumstances a more precise approach to the critical pressure reading points.

In either event, the pressure reading cycle is commenced when the operator depresses valve head 12. As shown in FIG. 2, such depression is made against the expansion action of spring 36, and causes valve stem 28, which is coupled to the upper portion of valve head 12 by set screw 28a, to be correspondingly depressed. This results in the downward movement of enlarged vlave stem member 28b from thesolid line position shown in FIG. 2 whereby cavity 30 is filled and the release path blocked, to the dashed line position 28b. The extent of the depression of valve head 12 in FIG. 2 is represented by the distance L, which is the separation between bottom surface 12a of valve head 12 and the upper edge of cam 14. Valve stem 28, and its enlarged portion-28b will also travel downward by this same distance L. This opens the pressure release path for pressurized air from the blood pressure cuff.

In particular, the pressurized air can now escape to atmosphere over a path from the cuff, through connecting tubing 18 and into bore 16b, following the path suggested by the dashed arrows at those locations. The air then proceeds through now unobstructed cavity 30 and into the passageway 32 which surrounds valve stem 28 through valve guide 40. The pressurized air emerges into internal spring housing chamber 34, and can now escape to atmosphere through aperture 38. This path will be available as long as valve head 12 is depressed into contact with cam 14. Should the operator release the depression force on valve head 12, spring 36 will return valve head 12 to its normal position illustrated in FIG. 1 and in full line in FIG. 2. This will cause enlarged valve stem member 2812 to return to its full line position in cavity 30, thereby blocking the access of the pressurized air to passageway 32. The return to the original position of valve head 12 could be accomplished during the pressure reading cycle if the operator is steppingdown the pressure so as to zero in" on the critical pressure reading points, or it could be done at the completion of the pressure reading cycle, but prior to the unattended deflation mode to .bedescribed below.

The Unattended Deflation Mode Feature When the pressure reading cycle has been completed, the operator will normally pay little attention to the valve device thereafter However, in order to commence a subsequent pressure reading cycle, or perhaps to repeat the pressure reading cycle on the same patient for checking purposes, itis important that all the remaining pressure in the cuff be removed therefrom. The present invention, as did my copending application. permits an operator to achieve the desired deflation without any significant effort or attention on his part.

In particular, referring to FIGS. 2 and 3, following the completion of the pressure reading cycle, the operator rotates valve head 12 about its vertical axis, i.e.,

about valve stem 28 which is rotatable within valve guide 40. After rotating valve head 12 so that flattened surface 12b will be disposed adjacent to, but spaced from, cam 14, as best shown in FIG. 3, the depression of valve head 12 will no longer bring its bottom surface 12a into contact with the upper edge of cam 14.111 stead, valve head 12 will bypass cam 14 on its downward movement. In so doing, the narrowed or frustoconical surface 34c forming the upper portion of the side walls of chamber 34 will come into engaging contact with upper peripheral rim 40b of valve guide 40. Because of the relative geometry of rim 40b and surface 34c, a wedging fit will occur therebetween, as indicated in FIG. 3. This fitis sufficient to retain valve permit any remaining pressurized air within the blood pressure cuff to rapidly proceed to atmosphere over the previously traced path. It is noted that although escape aperture 38 is directed to the left in FIG. 3, this change in orientation has no effect on the escape passageway, which is symmetrical with respect to the axis of rotation of valve head 12. Accordingly, all the remaining pressurized air will then quickly escape to atmosphere through escape aperture 38 while valve head 12 is in engagement with valve guide 40.

The retntion of valve head 12 in its downward position will continue indefinitely, until an operator takes steps to dislodeg valve head 12. Such dislodging is readily accomplished by the operators applying a lateral or rocking force to valve head. This permits the contact between surface 34c and rim 40b to be disturbed and spring 36 thereby elevates valve head 12 upward to the position illustrated in FIGS. 1 and 2.

The added features described in connection with the present invention permit the valve referred to herein to operate efficiently and even more reliably than that disclosed in my copending application. The improvements to the cam insure an ease of mounting as well as a certainty of setting, while still providing a selection of predetermined release rates. The check valve feature relies on an enlarged surface area against which pressure is applied, thereby developing substantial forces against the check valve member during and after inflation. This promotes an ease' of inflation while securely blocking any leakage of pressurized air. In achieving the rapid unattended deflation mode, the use of an internal narrowed bore in the valve head for contacting the valve guide provides a secure retaining arrangement-for the valve head, and yet permits the operator to readily dislodge the head when desired.

It is to be understood that the above-described embodiments are merely illustrative of the application of .the principles of this invention. Numerous variations may be devised by those skilled in the art without departing from the spirit or scope of the invention.

What is claimed is:

1. A release valve for controlling the release of fluid under pressure form a blood pressure measuirng apparatus comprising inflatable means and source means providing said inflatable means with said fluid under pressure, said release valve including a valve body communicating with said inflatable means for permitting fluid flow therebetween, valve means movable between open and closed positions with respect to said body for controlling the release of said fluid under pressure, said valve means including a control head movable to positions corresponding to said open and closed positions of said valve means, a guide element on said valve body cluding a chamber in said control head, said chamber having an opening and a first portion of a larger diameter than the outside periphery of said guide element to allow relative movement of said control head over said guide element, and a second portion narrowed to a smaller diameter than said outside periphery of said guide element to releasably couple said control head and said guide element against the action of said selfclosing means in a position corresponding to said open position of said valve means.

2. A release valve in accordance with claim 1 wherein said guide element has an upper surface supporting said self-closing means, and wherein said selfclosing means comprises a. spring housed within said chamber and bearing against said second portion of said chamber and. against said upper surface of said guide element to normally maintain said control head insaid closed position.

.3. A release valve in accordance with claim 1 wherein said second portion of said chamber includes a surface for engaging said upper surface of said guide element to establish a wedging fit between said control head and said outside periphery of said upper surface of said guide element to thereby retain said control head in said open position against the action of said 

1. A release valve for controlling the release of fluid under pressure form a blood pressure measuirng apparatus comprising inflatable means and source means providing said inflatable means with said fluid under pressure, said release valve including a valve body communicating with said inflatable means for permitting fluid flow therebetween, valve means movable between open and closed positions with respect to said body for controlling the release of said fluid under pressure, said valve means including a control head movable to positions corresponding to said open and closed positions of said valve means, a guide element on said valve body for directing the movement of said control head, self-closing means cooperating with said valve means to maintain said valve means in said closed position, and retaining means for releasably coupling said control head and said guide element to selectively maintain said valve means in said open position against the action of said self-closing means, said retaining means including a chamber in said control head, said chamber having an opening and a first portion of a larger diameter than the outside periphery of said guide element to allow relative movement of said control head over said guide element, and a second portion narrowed to a smaller diameter than said outside periphery of said guide element to releasably couple said control head and said guide element against the action of said self-closing means in a position corresponding to said open position of said valve means.
 2. A release valve in accordance with claim 1 wherein said guide element has an upper surface supporting said self-closing means, and wherein said self-closing means comprises a spring housed within said chamber and bearing against said second portion of said chamber and against said upper surface of said guide element to normally maintain said control head in said closed position.
 3. A release valve in accordance with claim 1 wherein said second portion of said chamber includes a surface for engaging said upper surface of said guide element to establish a wedging fit between said control head and said outside periphery of said upper surface of said guide element to thereby retain said control head in said open position against the action of said self-closing means.
 4. A release valve in accordance with claim 3 wherein said self-closing means is a spring and said engaging surface of said second portion of said chamber is tapered from said first portion to the end of said second portion.
 5. A release valve in accordance with claim 3 wherein said guide element is substantially cylindrical in shape and said first portion of said chamber is substantially circular to be accommodated over said guide element. 